In recent years, as wearable electronic products are becoming thinner and thinner, a traditional foamed sound-absorbing material cannot meet the demand for debugging or correction of sound-absorbing performance in the micro-speaker industry. Through constant development and trial of novel sound-absorbing materials, those skilled in the art discovered after verification that placing a porous sound-absorbing material in a rear cavity of a speaker can effectively improve the speaker's acoustic performance. The novel sound-absorbing material used at present comprises non-foamed sound-absorbing materials such as natural zeolite, activated carbon, white carbon black and zeolite powder with the silica-alumina ratio of 200 or above. During application, the above-mentioned powdery non-foamed sound-absorbing materials need to be prepared into particles at first. After that, the rear cavity of the speaker is filled with the sound-absorbing material particles of which the particle sizes can be adjusted in accordance with the size and the structure of the rear cavity of the speaker.
In this technical field, the commonly used granulation methods include extrusion, boiling granulation, spray drying, rolling into balls, etc. Particles made by extrusion, boiling granulation and rolling into balls are poor in strength, unsmooth in surface, uneven in size and limited in physical structure and performance, and have the main problems of small pore volumes and diameters. Consequently, sound-absorbing material particles made of these particles may have a limited sound-absorbing effect. Air circulation in the rear cavity of the speaker may also be influenced. Particles formed by spray drying are relatively smaller, non-uniform in particle size distribution and unsatisfactory in sound-absorbing effect. The processing process results in limited mass transfer efficiency and sound-absorbing effect of the sound-absorbing material particles and failure of a desired effect.
To sum up, it is necessary to improve the sound-absorbing material particles or a preparation method thereof. By improving the characteristics, including the uniformity of particle sizes, the structural strength, etc., of the sound-absorbing material particles, the sound-absorbing effect of the sound-absorbing material particles may be improved.